1. Field of the Invention
This invention is concerned with a novel mixture of phosphonate esters. It is also concerned with fire retardant polymer compositions containing them.
2. Description of the Prior Art
In U.S. Pat. No. 3,027,349 there is disclosed a mixed phosphite-phosphonate polymeric material produced by isomerizing tris(2-chloroethyl)phosphite at temperatures greater than 180.degree. C. (180.degree.-300.degree. C.) and their use as flame retardants. The polymeric structures (high boiling phosphonate) of this invention do not have the phosphite structure in the molecule, i.e., all the phosphorus atoms in the compound are pentavalent phosphorus.